The UCSD Retrovirology Laboratory has made important contributions to the success of the UCSD ACTU and to the retrovirology effort of the overall ACTG program. Some of the accomplishments of the Retrovirology Laboratory have helped to expand the role of virologic markers in clinical trials and to influence the direction of specific ongoing and new ACTG protocols. The Laboratory has worked particularly closely with ACTG investigators participating in Phase I-II studies and has frequently played an important role in helping to guide investigators in future studies. Specimens from both the UCSD Adult and Pediatric ACTUs are processed by the Retrovirology Laboratory which has been consistently certified for HIV isolation and p24 antigen determinations. The Specific Aims of the UCSD Retrovirology Laboratory are: (1) To apply standardized, reproducible and quality- controlled assays of HIV infection as virologic markers in patients participating in ACTG protocols; (2) To provide essential virologic data to help guide clinical investigators in determining future directions of Phase I-II antiretroviral studies; (3) To evaluate the utility of new virologic assays for monitoring the response of patients participating in antiretroviral studies; and (4) To assist in the development of novel virologic assays which can be applied to monitor patients receiving antiretroviral therapy by providing well-characterized and properly stored specimens. Because of the size of the UCSD ACTU, the Retrovirology Laboratory proposes to process annually 500 standard HIV cultures, 350 quantitative cell dilution cultures, 350 plasma viremia cultures, and 24,000 plasma and culture supernatant p24 antigen determinations. The continued participation of the UCSD Retrovirology Laboratory in the UCSD ACTU will help contribute to the development of improved treatments for patients infected with HIV.